karolh

I plan on purchasing several servos as replacement units in a couple of my old models and would like to use Hitec HS-325HB and 635HB units. I have however been advised not to do so as they both use Karbonite gears which have a history of stripping fairly easily, and instead should choose a servo with nylon gears. Is this a myth or is there some truth to it, as I would hate to make a bad choice here.

Karol

BarracudaHockey

My Feedback: (11)

Karbonite is a bit more brittle but its nothing more than hitecs name for plastic.

I've never stripped a karbonite gear where I wouldnt have stripped a nylon gear.

Ed

Yes, I have read the horror stories about Karbonite, but I still have 635's in use on 3 different aircraft, and all perform flawlessly. I guess it depends on where, and how used.

> Jim

XJet

Karbonite is just a harder more brittle form of plastic (I suspect it's got some carbon impregnated in it).

As a result, it's much harder wearing and deforms less under load than nylon, however it can be rather fragile when exposed to shocks such as those experienced from hangar-rash, flutter or the vibration of a large gasser or 4-stroke engine.

I use quite a few of Hitec's HS475HB servos which have a karbonite geartrain and have never had a single failure -- but I only use them on 40-90 sized planes.

On anything that requires more strength than nylon, I go straight to metal gears. Karbonite was a bit of a self-delusion by Hitec's marketing department. It's not bad, but it's not what it was cracked up to be and in fact nylon gears are "tougher".

Geistware

My Feedback: (16)

Karbonite will perform better than nylon gears.
They do not perform better than metal.
You can use Karbonite if the suface load/impact is less than 12lbs.
I would imagine that nylon is equal to this.

karolh

Here in Jamaica though our hobby is quite vibrant, we don't often have the luxury of experimenting as there is no hobby shop here. All the stuff we need comes from overseas, mostly from the US, so we try to get it right the first time around. Thanks to all for your comments.

Karol

Zeeb

My Feedback: (41)

Geist,

I thought Hitec did not recommend Karbonite for models weighing more than 12lbs. not anticipated surface load?

Besides the fact that I've not seen a gasser that light which makes it kind of a moot point, I don't think Hitec recommends them for gas engines either due to the higher vibration levels?

Just curious if I've mis-read something?

karolh

If that is true, maybe Hitec should make a greater effort to advise customers of usage limits as it relates to their products, so as to avoid misuse.

For example all model manufacturers give a specific engine range for their products so as to virtually guarantee satisfactory powered flight performance. Judging from some of the earliest Karbonite ads, it seemed as if it was going to be the best thing since sliced bread.

Karol

Brian Smith

My Feedback: (117)

A few months back I bought 475HB carbonite servos for my G38 powered ARF Big Stick.. On the 3rd flight one stripped.. I called Hitec and Mike replaced them with 645s and said Hitec does not recomend Carbonite gear servos for gas models and only glo motors 60 size and smaller. Maybe there have been changes since. That is all the "facts" I have.. Brian

karolh

This has been very enlightning, as I would most certaintly have made a really big boo boo as some of the replacement servos are for use in a 1/4 scale gas powered sport model. I think I will stick to the evils that I know.....nylon or metal.

Karol

Brian Smith

My Feedback: (117)

I have been very pleased with Hitec products and servos over the years.. Bet I have bought hundreds.. I still use only 645s in all my "GAS" powered models.. I found some on e-bay new for $31 and bought 12.. If you look around they can be found at a good price.. Brian

Geistware

My Feedback: (16)

Karbonite is not recommend for more than 12lbs per servo.
So for a 24 lb bird, you need to have two servos per control surface.
Violent 3D may require more.
I have used 4 servos for ailerons (2 per side) with no problems.

karolh

I too have used several Hitec products including their servos and have had trouble free service, but have never used any with Karbonite gears.

karol

Brian Smith

My Feedback: (117)

I think it say on the Hitec site that 635HBs are "UP TO 12 Pound models" Brian

Geistware

My Feedback: (16)

You are 100% correct.
This what it says on the 635HB
Applications: Sport to high performance aircraft to 12 lbs.

I thought we were talking about Karbonite in general
If you look at the HS-6985HB it says the following:
Applications: Sport or high performance Aircraft to 12lbs.

Note:Larger aircraft can be flown with Karbonite geared servos if ganged together. Hitec recommends a maximum of 12lbs per servo, per control surface. (I.E. A 24 lb plane should use two servos per surface.)

So I was speaking in general for the gear train material.
Sorry if I was leading the thread off topic.

Brian Smith

My Feedback: (117)

No I don't think you were at all. Guess I'm just leary of carbonite as it almost cost me a model.. You do a lot for the RC community so carry on. Brian

BarracudaHockey

My Feedback: (11)

I know that one of the problems they were having is people using locktite on the servo arm screw. Locktite is very aggressive towards plastic and was making the output shaft brittle and causing failures.

RVman

The karbonites wear better, my 475's have zero slop in them after many flights unlike the nylon gear servos. I use them in 40-60 size planes.

Geistware

My Feedback: (16)

Brian,
Thanks for the compliment. [8D]

Hitec at one time also recommended a longer screw than the supplied 8mm length.
I have used 5975 servos in my 33% model for the ailerons.
I usually send in my servos about every 150 flights or so.
I can say I have at least that many flights on my Cap 232 with those servos and never had a problem.

YUKONFLYR

Amazing - Two years have past and if you look at a HS635HB it still does not have anything on the box limiting it to 12 pounds. In fact the servo box says how tough Karbonite is and rates the servo up to 1/4 scale. After my buddy lost his 10 pound Mustang, Karbonite elevator servo gear train failed, his confidence in Hitec is diminished.

I see more and more servos going Karbonite in the Hitec lineup.......................Think I will look for Non - Karbonite servos.

RCAddiction

My Feedback: (87)

Karbonite is nothing much more than fiber-filled nylon. It's just a little bit stronger than unfilled (white) nylon. Chances are good the the 10lb Mustang would have failed with a standard white nylon gear even faster.

Yes - Use Karbonite anywhere you'd think Nylon is ok, and it should wear longer than plain white nylon gears.
No - never substitute Karbonite for something that demands a metal gear.

pilotpete2

When I switched to Karbonite gears for my 2 stroke 90.Goldberg Extra 300 (BIY kit) back when this thread started, I was somewhat concerned. Halfway trough the third season all I can say is they're tuff stuff[8D]. The spare gears I bought back then are sitting in my parts bin. The servo gears even survived a mid-air that wiped out the wing one inch past the right aileron servo, the aileron was completely ripped out and dangling by the linkage, no broken teeth. The plane has been beaten pretty hard, but no servo problems with 5 325HB's and one 475HB on rudder. I should also add I'm always banging a control surface when handling the planes.[&o]
Pete

Pippin

My LHS would not recommend carbonite for gassers. The people there (some of them flying F3A-X competition) would only use carbonite gears in gliders. They say, the only plus of carbonite over nylon is the quiter gear. If you fly a glider this is the real and only advantage of carbonite. Otherwise they would only recommend nylon or metal, depanding on size and engine.

pilotpete2

I have to disagree. The advantage of Karbonite gears is less wear than metal or nylon gears.
If you mean gasoline/ignition when you say "gasser" I would agree, for glow powered sport models, the Karbonite gears work very well.
If anything, nylon gears are the quietest
Pete

Pippin

Yes, I mentioned gasoline (two stroke engines). Less wear would mean longe life? Thats right.
I do not see an issue too, unless you go 50ccm size engines. The only problem is see are shear forces. It´s not the strong point of any carbon application.